1. Field of the Invention
The present invention relates to a power supply suitable for a data processor, etc. and particularly to a rectifier-type direct-current power supply having an inrush current suppressing circuit for preventing an inrush current at the time of closing the power supply.
2. Description of the Related Art
When directly impressing a power supply voltage to the input section of a rectifier-type direct-current power supply, the large-inrush current, which is determined by the minimum impedance of the circuit as seen from the input section, flows instantaneously and tends to cause damage to bridge rectifiers. Even with the inrush current limiting circuits that are commonly used to suppress inrush current, there is the problem that in cases of repeated reclosing within a short time interval after cutting alternating-current input voltage, the inrush current suppressing circuit cannot be caused to operate due to damage caused by heat generation of the circuit. Japanese Patent Laid-open No. 17517/92 discloses a technique by which, upon start-up, a smoothing capacitor is first charged to a prescribed charge voltage by a charging apparatus by way of a current-limiting resistor, upon which a magnetic contactor of a main rectifying circuit is closed, thereby preventing inflow of a large inrush current to the smoothing capacitor. However, even this method fails to function if the impedance of load 13 is extremely low.